1. Field of the Invention
This invention relates to vacuum cleaner filtration. In one of its aspects, the invention relates to a filtration assembly for a vacuum cleaner. In another of its aspects, the invention relates to a fine particle filter for filtering particles downstream from a primary particle separator. In yet another of its aspects, the invention relates to a filtration assembly for a vacuum cleaner.
2. Description of the Related Art
Upright vacuum cleaners have a main filtration or separation assembly for separating dirt and debris from air drawn into the vacuum cleaner by suction force. The main filtration assembly typically comprises a conventional filter bag or a centrifugal separator. Vacuum cleaners with a centrifugal separator may employ a cyclone separator as a main filtration or separation assembly, such as a frusto-conical shaped separator, while others use high-speed rotational motion of the air/dirt in a cylindrical separator to separate the dirt by centrifugal force. Typically, working air enters and exits at an upper portion of the cyclone separator and the bottom portion of the cyclone separator is used to collect debris. It is further known to employ multiple serial cyclone separators to improve the collection of fine debris particles that may not be collected by a single separator.
Vacuum cleaners further have at least one motor/fan assembly for generating suction to draw air and debris into the vacuum cleaner. In some models, a second motor/fan assembly is used to drive an agitator, such as a brushroll. Air to cool to the motor/fan assemblies is drawn into the vacuum cleaner and subsequently exhausted from the housing through separate ports in vacuum cleaner housing. As the air passes through the motor, carbon dust discharged from the motor brushes can become entrained in the air and thus also exhausted from the vacuum cleaner, leading to contamination of the home environment. Some effort has been made to filter the motor cooling air after it has passed through the vacuum cleaner. A second or auxiliary filtration assembly comprising a “mechanical” filter can be employed for this purpose. A filter can be placed at the inlet or exhaust port to remove carbon dust from the motor cooling air, however, this filter adds expense and bulk to the vacuum cleaner. A high efficiency particle arrestor (HEPA) filter is commonly used for the second filtration assembly.
Even those vacuum cleaners having means to collect fine debris and to filter the motor cooling air after it passes through the motor do not protect the home environment from certain bacteria and molds that may be drawn from a carpet or other surface and rendered airborne by the exhaust form the vacuum cleaner, spreading unpleasant odors and unhealthy bacteria. The vacuum cleaner can suction up bacteria and mold, but then these undesirable items are exhausted back into the home environment because their small size prohibits collection by a cyclone separator.